Many products, both hardware and software, have diagnostic tools or applications for communicating with them. When such products are located at customer sites, there is no way to use these tools except to send a service technician on-site to diagnose and repair any problems.
Tunneling solutions exist that provide a diagnostic program with access to a remote application. However, such tunneling solutions require a server at each site to provide access to applications behind its firewall. Since the additional server requires additional administration and maintenance at each site, it is an additional burden to end-users or customers.
Furthermore, and perhaps more significantly, installing a server at each site that provides tunnel access to a local network also has security risks. For example, such a server is addressable via the Internet, and thus is a target to break into an otherwise secure network.